24 FLORA INDICA. all this proves nothing; but when wo add the tacit acquies- cence of Robert Brown, and of all other botanists who have lived amid a tropical vegetation, and devoted thom*rlvrs to its study, it will not be considered surprising that TO should suspect such evidence as has hitherto been adduced by local observers only, and in very limited areas. The subject of hybridization is however well worthy of the attention of the tropical botanist; and both in liis'^nrdim and in the field, he should keep his attention always alive- to the importance of observing every phenomenon that may bear upon its agency, and should institute operations that will throw light upon the subject. B. Qit, Variation of Although the researches of naturalists have not hitherto led to the detection of those laws in ohedienee to \vltieh many Species of plants vary mueh in one climate and le&a in others, or remain constant throughout many cliimitic conditions, they indicate the operation of certain general laws, whose efttrts arc as follows : — 1, Contiguous areas, with different climates, are peopled by different species of plants, and not by the same under ditler- cut forms. 2. Similar climates iu distant areas arc not jxwpit'ii by the same or even similar species, but generally by different natural ordcra of plants, 3. Both contiguous and remote area* contain a certain admixture of species common to two t>r all of them, which retain their individuality under every diungp gf climate. These aro generally admitted facts; there arc however ex- ceptions, upon which are based the arguments for attributing to climatic effects the creation of many K|>ecica from cue vari- able type. Careful observation reveals many such exception*; and the tendency which plants display to revert to one 'typical species. The contrary inference, ttat speck* aro aubjoet to * w**$fa amount of rariatiou, does not seem to have owmrwd to him.